AVS 64th International Symposium & Exhibition
    Electronic Materials and Photonics Division Thursday Sessions
       Session EM+NS-ThA

Paper EM+NS-ThA2
Growth and Characterization of α-, β-, and ε-Ga2O3 Epitaxial Layers

Thursday, November 2, 2017, 2:40 pm, Room 14

Session: Wide and Ultra-wide Band Gap Materials for Electronic Devices: Growth, Modeling, and Properties
Presenter: Lisa Porter, Carnegie Mellon University
Authors: L.M. Porter, Carnegie Mellon University
Y. Yao, Carnegie Mellon University
L.A.M. Lyle, Carnegie Mellon University
S. Okur, Structured Materials Industries, Inc.
G.S. Tompa, Structured Materials Industries, Inc.
T. Salagaj, Structured Materials Industries, Inc.
N. Sbrockey, Structured Materials Industries, Inc.
Correspondent: Click to Email
Increasing global demand for energy makes urgent the need for highly efficient high-power electronics for energy conversion and transport. Although silicon devices have been traditionally used for high-power electronics, wide bandgap semiconductors (e.g., SiC and GaN) are much more efficient for these applications, because they can withstand higher electric fields with less material and reduced energy loss. However, the substrates of both materials are still very expensive. A very promising alternative to SiC and GaN is gallium oxide, Ga2O3, which has an even larger bandgap than the former two materials. The availability of this material presents new possibilities for disruptive devices and technologies that could translate to even greater energy efficiencies at lower cost than predicted for SiC and GaN. Polished 2-in diameter, single-crystal wafers of the monoclinic β-phase can be grown using melt-growth methods and are commercially available. However, there is increasing interest in the other Ga2O3 phases, particularly the metastable corundum-structured α- and hexagonal-structured ε-Ga2O3 phases because of their higher symmetry and simpler epitaxial relations to c-plane sapphire, in addition to the possibility of producing functional heterostructures or tunable bandgaps through alloying. We have successfully grown epitaxial films of α-, β- and ε-phases on c-plane sapphire using different precursors and growth conditions. The α- and ε-phases have generally been reported in the literature to form at lower growth temperatures than the β-phase. However, we observed a change in phase formation at the same growth temperature by changing our growth technique and Ga precursor from metalorganic chemical vapor deposition (MOCVD) and trimethlygallium to halide vapor phase epitaxy (HVPE) and gallium chloride. Data from x-ray diffraction, scanning electron microscopy and high-resolution transmission electron microscopy will be presented to illustrate the different epitaxial films and orientation relationships. The results of secondary ion mass spectrometry depth profiles, which showed compositional differences within the different phases, will also be presented. The authors wish to acknowledge the Office of Naval Research under contract no. N00014-16-P2059.